System and Method For Fusing Chemical Detectors

ABSTRACT

Two complementary approaches to the science of IMS technology, IMS and differential IMS (DIMS), are combined into a single instrument to provide improvements in interference rejection without sacrificing detection sensitivity. The technology is applicable to, inter alia, the analysis of trace quantities of toxic or otherwise dangerous organic chemical materials. The approach improves both sensitivity and specificity (interference rejection) of field detection instrumentation.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. application Ser. No.14/474,559, filed Sep. 2, 2014, titled “System and Method For FusingChemical Detectors” which claims the benefit of priority to similarlytitled U.S. Provisional Patent Application Ser. No. 61/871,927, filedAug. 30, 2013, the contents of which are incorporated herein byreference in their entirety.

BACKGROUND OF THE EMBODIMENTS

1. Field of the Embodiments

The embodiments are generally directed to chemical detectors and moreparticularly to an improved chemical detector which fuses previouslyindependent approaches to ion mobility spectrometry (IMS) into a singledetector.

2. Description of Related Art

Ion Mobility Spectrometry (IMS) has been the primary technology forchemical warfare agent detection for at least 30 years. Screening ofairport passengers for explosives and illegal drugs has relied on IMSfor about the same period. There are hundreds of thousands ion mobilityspectrometers in use throughout the world. Instrumentation advantages interms of small size and low electrical power requirements coupled withexcellent sensitivity and spectrometric specificity make IMS an idealtechnology for field detectors. As with any analytical chemistrytechnique, improved sensitivity and specificity without sacrificingsize, weight, power and cost benefits are continually sought. The numberone complaint by users of IMS instrumentation is that the systems areprone to interferences. As requirements for field detection of variousand “non-traditional” substances increase, complaints of interferencesare likely to increase.

Ion Mobility Spectrometry (IMS) is the study of the motion of gas-phaseions under influence of electric fields. Several methods for study onthe ion motion are used throughout the IMS field. A combination or“fusion” of two of these methods is proposed—the IMS methods will bereferred to here as “Linear” IMS or just IMS (the traditional term) and“Differential” IMS or DIMS. A detailed treatment of theory and practiceof IMS can be found in the book “Ion Mobility Spectrometry—2^(nd)Edition” by G. A. Eiceman and Z. Karpas, CRC Press Taylor & FrancisGroup, Boca Raton (2005). The substance of this reference is consideredto be known to those having skill in the present art and is incorporatedherein by reference.

Currently, existing field detectors use either IMS or DIMS, but notboth. For example, the LCD 3.3 (Light Weight Chemical Detector) fromSmiths Detection uses IMS processing. While the JUNO detector developedby Chemring Detection Systems is exemplary of a previously proposeddetector that uses DIMS processing for detection of CWA and low vaporpressure agents.

There is no literature record of IMS and DIMS sensor and data fusionwhere the two complementary technologies have been operated in parallel.There have been previous attempts to fuse IMS and DIMS technologies asdescribed in E. Nazarov, et al.; “Miniature DMS-IMS Detector forEnhanced Resolving Power;” 16th International Conference on Ion MobilitySpectrometry, Mikkeli, Finland; July 2007 and in A. G. Anderson, et al;“DMS-IMS2, GC-DMS, DMS-MS: DMS hybrid devices combining orthogonalprinciples of separation for challenging applications;” Chemical,Biological, Radiological, Nuclear, and Explosives (CBRNE) Sensing IX.Edited by A. W. Fountain, P. J Gardner; Proceedings of the SPIE, Volume6954, pp. 69540H-69540H-12 (2008). The described approach used a DIMSdevice for rapid separation of target ions and introduction of separatedions into two IMS instruments. A DIMS device separates positive andnegative ions simultaneously. Positively charged ions are directed intoan IMS device which is appropriately biased and negative ions aredirected into the other IMS device. While this design, theoretically,provides for enhanced separation of analyte ions—such is not necessarilythe case. Referring to FIG. 3 it can be seen that if the DIMS deviceselects small ions for analysis by the IMS systems, no resolution isgained since IMS cannot effectively separate small ions. For large ionsthere is little to no separation by the DIMS system, the IMS system isrelied on to separate the ions. In both cases, sensitivity is sacrificeddue to ion loses between the mobility spectrometers with insignificantimprovements in resolution.

SUMMARY OF THE EMBODIMENTS

The present embodiments combine or “fuse” two complementary approachesto the science of IMS technology into a single instrument to provideimprovements in interference rejection without sacrificing detectionsensitivity. The two techniques are referred to as IMS and differentialIMS (DIMS). The technology is applicable to, inter alia, the analysis oftrace quantities of toxic or otherwise dangerous organic chemicalmaterials. The approach described herein improves both sensitivity andspecificity (interference rejection) of field detection instrumentation.

The embodiments combine the two techniques into a single instrument andcombine the data outputs of the two technologies through the use ofadvanced signal processing techniques to take advantage of thecomplementary nature of the two approaches. The combination is such thateach IMS technique processes an ingested sample independently, i.e., inparallel, and then the data is combined to give a single result withexcellent sensitivity and interference rejection.

More particularly, in a first exemplary embodiment, a chemical agentdetector includes: an ionization chamber including at least one ionsource for generating positive and negative ions from a sample; a firstion mobility spectrometry cell integrated with the ionization chamberfor receiving at least a first portion of the positive ions therefrom; asecond ion mobility spectrometry cell integrated with the ionizationchamber for receiving at least a first portion of the negative ionstherefrom; a differential ion mobility spectrometry cell integrated withthe ionization chamber for receiving at least a second portion of thepositive ions and at least a second portion of the negative ionstherefrom; and a processor for separately receiving first detection datafrom the first ion mobility spectrometry cell, second data from thesecond ion mobility spectrometry cell, and third data from thedifferential ion mobility spectrometry cell and processing the first,second and third detection data to determine presence of one or morechemical agents in the sample.

In a second exemplary embodiment, a process for parallel chemical agentdetection includes: introducing a sample into an ionization chamber;ionizing the sample to create positive and negative ions; receiving at afirst end of a first ion mobility spectrometry cell from the ionizationchamber at least a portion of the positive ions; receiving at a firstend of a second ion mobility spectrometry cell from the ionizationchamber at least a portion of the negative ions; introducing a drift gasinto a second end of each of the first and second ion mobilityspectrometry cells, wherein the drift gas flows in an opposite directionfrom a flow of the portions of positive and negative ions in the firstand second ion mobility spectrometry cells; receiving at a first end ofa differential ion mobility spectrometry cell a second portion of eachof the positive and negative ions from the ionization chamber and afirst portion of the drift gas, wherein the first portion of the driftgas and the second portion of each of the positive and negative ionsflow in the same direction within the differential ion mobilityspectrometry cell; generating first and second chemical agent detectiondata at first and second detectors located at the second end of each ofthe first and second ion mobility spectrometry cells; generating thirdchemical agent detection data at a third detector associated with thedifferential ion mobility spectrometry cell; processing by a processingsystem the first, second and third chemical agent detection datadetermine presence of one or more chemical agents in the sample.

In a third exemplary embodiment, a hand-held chemical agent detectorincludes: an ionization chamber including at least one ion source forgenerating positive and negative ions from a sample, wherein thedimensions of the ionization chamber are less than 1 cm width, 2.5 cmlength and 2.0 cm height; a first and second ion mobility spectrometrycells integrated with the ionization chamber for receiving at least afirst portion of the positive and negative ions therefrom, wherein thedimensions of the first and second ion mobility spectrometry cells areless than 2.5 cm width, 2.0 cm length and 2.5 cm height; and adifferential ion mobility spectrometry cell integrated with theionization chamber for receiving at least a second portion of thepositive ions and at least a second portion of the negative ionstherefrom, wherein the dimensions of the differential ion mobilityspectrometry cell are less than 1 cm width, 1.0 cm length and 3.0 cmheight.

BRIEF DESCRIPTION OF THE FIGURES

The Summary of the Embodiments, as well as the following DetailedDescription, is best understood when read in conjunction with thefollowing exemplary drawings:

FIG. 1 is a prior art schematic showing separation of ions in an IMSsystem;

FIG. 2 is a prior art schematic showing separation of ions in a DIMSsystem;

FIG. 3 illustrates that ion separation or spectral resolution of IMS andDIMS is dependent on the size of analyte ions;

FIG. 4 is a schematic showing a hybrid IMS-DIMS system in accordancewith an embodiment herein;

FIGS. 5a and 5b are schematics showing a hybrid IMS-DIMS system havingtwo IMS cells and scrubber configuration in accordance with anembodiment herein;

FIGS. 6a and 6b are schematics showing a more detailed schematic of FIG.5a with differing ionization sources; and

FIG. 7 is a schematic showing a hybrid IMSx2 mass spectrometer system inaccordance with an embodiment herein;

FIGS. 8a and 8b are isometric views of an IMSx2 system in accordancewith embodiments described herein;

FIGS. 9a-9f provide views with exemplary dimensional information for keycomponents of the IMSx2 system;

FIGS. 10a and 10b are isometric views of a first exemplary ionizationchamber for use in the IMSx2 system described herein; and

FIGS. 11a and 11b are isometric views of a first exemplary ionizationchamber for use in the IMSx2 system described herein.

DETAILED DESCRIPTION

With regard to IMS, the terminal velocity of an ion drifting under theinfluence of the electric field is proportional to the electric fieldstrength;

v_(d)=KE  (1)

where v_(d) is the ion's terminal velocity, E is the electric fieldstrength and the proportionality constant, K, is defined as ionmobility. IMS is the traditional term used for linear field dependenceIMS—this terminology will continue here.

Most ion mobility spectrometers are governed by Equation (1) which is anexcellent approximation at relatively low electric field strengths, fromzero to a few hundred volts per cm. At high electric field strengthsupwards of a few kilovolts per cm, ion mobility cannot be represented asa constant value—ion mobility, K, takes the form

K(E/N)=K(0)[1+α(E/N)]  (2)

where K(0) is the ion mobility under zero (and low) field conditions andE/N is the electric field normalized for pressure—the coefficient a isused to describe the dependence of ion mobility on high electric fields.To differentiate field-dependent ion mobility spectrometry from the moretraditional linear ion mobility spectrometry the term Differential IonMobility Spectrometry or DIMS is used to indicate that ion mobility isvariable with electric field strength. It should be noted DIMS issometimes referenced by other names including Field Asymmetric IonMobility Spectrometry (FAIMS) and Field Ion Spectrometry (FIS). DIMS isthe term used herein.

It is electric field dependence and the bases of operation thatstimulated the idea for development of the embodiments described herein.IMS operates using DC electric fields and DIMS operates using acombination of RF and DC electric fields. Differences in separation ofatmospheric pressure ions are significant. Although the techniques arenot orthogonal in the strict sense, they are such that the fusion of ionmobility spectra will result in signal attributes that will enhancefalse alarm reduction and, in some cases, eliminate false alarmsaltogether.

Following FIG. 1 from upper left to upper center down to lower centerand finally to lower right the sequence of events is as follows: (1)“primary” ions are formed as a result of electric discharge or ionizingradiation, primary ions react with neutral species (target analytes) toform analyte ions and these ions drift into a reaction region where theyare “trapped” by a grid that is electrically biased to prevent ions frompassing through; (2) periodically the grid voltage is lowered for ashort period (typically one to two hundred microseconds) which allows apacket of ions to enter the separation or drift region; (3) this packetof moves through the drift region under the influence of a constantelectric field, E, where separation occurs according to the size of theions and the charge on the ions—the smaller ions move faster than thelarger ions; (4) as ions impact an ion collector a current is created inexternal circuitry and the variation of the ion current with “drifttime” is an ion mobility spectrum—typically the spectrum drift time is15-50 microseconds. This sequence is repeated as required by theapplication.

From left to right in FIG. 2: (1) analyte laden air flows through asource of ionization, usually radioactivity, producing primary ions;reactions between primary ions and neutral analyte molecules areidentical with the reactions in IMS; (2) ions continue to flow between aset of closely spaced (<1 mm) parallel plates or concentric cylinders;(3) as the ions flow between the plates they are subjected to anasymmetric RF field, the dispersion field, that varies at constantfrequency, positively and negatively up to several kilovolts per cmwherein the high voltage part of the RF cycle is twice the amplitude andhalf the period of the low voltage part; (4) the RF field issuperimposed on a DC voltage that is scanned over a few 10's of voltspositively and negatively; (3,4) at a unique combination of RFdispersion voltage and DC compensation voltage an ionic species of aspecific size and charge has a stable flight path through the plates,others impact walls and are neutralized—as the DC voltage is scannedother ions come into stability; (5) the stable ions are then directedinto ion collectors that are biased to receive appropriately chargedions to create spectra, differential ion mobility spectra. The peakamplitude of the RF voltage is varied and another spectrum is obtained.

Experiment has shown that ion separation or spectral resolution of IMSand DIMS is dependent on the size of analyte ions. FIG. 3 illustratesthis point. The left hand side of FIG. 3 indicates that as the size ofan analyte ion increases, separation of IMS analyte ion peaks increaseswhile DIMS exhibits the opposite relationship. The right hand side ofFIG. 3 is another representation of this characteristic—large ions tendto toward more overlap in DIMS, small ions tend to toward more overlapin IMS. Resolution can be adjusted through variation of electric fields,total drift voltage in IMS and RF voltage amplitude in DIMS. Reagent ionintensity, gate pulse width and repetition rate, length and spacing ofDIMS electrodes, and other parameters affect sensitivity andresolution—some effects are in opposite directions. As in otheranalytical techniques, an improvement in resolution results indecreasing sensitivity.

The present embodiments utilize the two mobility spectrometry techniquesdescribed herein in parallel to take advantage of separation orresolution capabilities of both. Resolution of each of the techniques ismaintained and there are no ion losses between the spectrometers. Thedetectors acting together as a “fused” sensor provide analyticalchemical power for successful detection and identification of, forexample, unknown bulk explosives (UBE) and homemade explosives (HME) inaddition to detection of CW agents, TICs/TIMs, NTA, explosives and otherdangerous materials. Sensitivity and response time are comparable.

Referring to exemplary configurations of the fused IMS and DIMS sensortechnologies shown in FIGS. 4 through 11, in order to realize the fulladvantages of fusing the complementary aspects of the two technologies,the IMS and DIMS cells are such that a single ionization source and anion-molecule reaction single reaction region is common to both.Exemplary DIMS cells which may be modified for use with the presentembodiments are described in U.S. Pat. Nos. 8,146,404, 7,576,322 and7,579,589. Taking advantage of common components allows for reducedfootprint and implementation through a hand-held device.

In a first embodiment shown in FIG. 4, the detector 100 includes asingle IMS cell 105 to switch between positive and negative ion modesand a single DIMS cell 110. In the alternative embodiments of FIGS. 5through 8, there are two IMS cells 205 a and 205 b, one positive and onenegative to a single DIMS 210 (the entire detector system 200 beingreferred to as IMSx2). The internal gas flow requirement of IMS and DIMSdetector cells lends itself to the illustrated configurations. The IMSprocess requires that a drift gas flow in the opposite direction of theion current while DIMS requires that this carrier gas flow is in thesame direction as the ion current. In FIG. 4, the drift gas in the IMSbecomes the carrier gas in the DIMS. A single ion source 115 will serveto initiate the necessary ion-molecule chemistry for both cells. Asingle gas scrubber 120 will suffice for both cells.

In FIGS. 5a and 5b , the IMSx2 system 200 includes two IMS cells 205 aand 205 b, one positive and one negative, and a single DIMS 210 as wellas dual scrubbers 220 a, 220 b. The IMSx2 system 200 is able to operateusing a single ion source 215 for all three cells. Alternatively, a dualion source configuration is also contemplated by one or moreembodiments. Similarly, FIGS. 6a and 7 also illustrate IMSx2 system 200including two IMS cells 205 a and 205 b, one positive and one negative,a single DIMS 210 and a single ion source 215. In the ionization space225 in the vicinity of the single ion source 215, “primary” ions areformed as a result of electric discharge or ionizing radiation. Thesingle ion source may be optimized in accordance with other systemparameters and intended use for the system and may include, but is notlimited to, corona discharge, atmospheric pressure photoionization(APPI), electrospray ionization (ESI), a radioactive source,laser-induced discharge and MALDI (matrix-assisted laser-desorptionionization). An analyte sample 230 is introduced to the system 200through an inlet 235 and directed to ionization space 225. Thecharacteristics of the inlet 235 vary in accordance with the type of ionsource as highlighted further below and in the figures.

Further to FIGS. 6a, 6b and 7, the inlet 235 configuration may vary inaccordance with the configuration of the ionization source 215. That is,depending on the type of ionization source 215 that is utilized, theinlet 235 may be a membrane configuration 235 a as shown in FIG. 6a whenthe ion source 215 is a radiation ion source 215 a or the inlet 235 maybe a pulsed inlet 235 b as shown in FIG. 6b when the ion source 215 is acorona discharge source 215 b. The individual IMS cells 205 a and 205 breceive respective positive and negative ions from the ionization space225 into drift chambers or tubes 240 a, 240 b (not shown) and detectionoccurs at detectors 245 a, 245 b located at the opposite ends of thedrift tubes 240 a, 240 b.

The configuration of the ion source 215 and ionization space 225 may beany configuration that allows for dual polarity ionization of theanalyte sample. For example, the dual mode ion configuration describedin U.S. Pat. No. 7,259,369 to Scott et al. or a variation thereof ascontemplated by one skilled in the art may be utilized. U.S. Pat. No.7,259,369 is incorporated herein by reference in its entirety. In aparticular embodiment, the ion source 215 includes positive and negativeDC corona ionization in ionization space 225. Additional structuraldetails and dimensions of the ionization space (or chamber) 225 arediscussed further below and illustrated in various figures.

The drift chambers or tubes 240 a, 240 b of the individual IMS cells 205a and 205 b are integrated with the ionization space 225 in anyconfiguration which facilitates the detection of both positively andnegatively charged ions produced from a common source. Exemplaryconfigurations are described in, by way of example, U.S. 4,445,038 toSpangler et al., U.S. Pat. No. 5,543,331 to Puumalainen and U.S. Pat.No. 7,576,321 to Wu which are incorporated herein by reference in theirentireties. Individual IMS cells such as those embodied in the ExcellimsHPIMS products are exemplary of the components and operationalcharacteristics which are contemplated for use as the cells 205 a and205 b of the present embodiments. For exemplary purposes, the driftcurrent (EDC) through the drift tubes which are on the order of a fewcentimeters in length is measured to be approximately 200 V/cm. The RFvoltage amplitude (ERF max) in the DIMS component is in the approximaterange of 0-20 kV/cm with an electrode spacing of ≦1 mm.

FIG. 7 illustrates yet another embodiment which is an IMSx2—MassSpectrometry hybrid. DIMS, also known as FAIMS (Field Asymmetric IonMobility Spectrometry), interfaces 250 have been developed for massspectrometers 255. One example is the FAIMS Interface for the ThermoScientific series of mass spectrometers and another is the ultraFAIMS MSinterface offered by Owlstone Nanotech. It is anticipated that real timeresponses result from the IMSx2 system with “good” specificity and“great” sensitivity. Responses with “good” sensitivity and “great”specificity are derived from the IMSx2-MS system with longer responsetimes.

Referring to FIGS. 8a and 8b , an exemplary isometric view of an IMSx2system configuration 200 in accordance with an embodiment is shown. Asdescribed above and shown in the view of FIG. 8a , the system includes ahigh voltage source 260, DIMS 210, ionization chamber 225, IMS sensorarrays 205 a, 205 b, and flow control components 265. In the second viewshown in FIG. 8b , the carbon drift gas scrubbers 220 a, 220 b areshown. Additionally, FIG. 8b shows the system control panel, includingon/off switch and, data port, the latter of which is critical torelaying sensor/detector data from the IMS cells and DIMS to theprocessing system 350, which includes fusion software for fusing thereceived data and making chemical detection determinations basedthereon. For exemplary purposes, the dimensions of the power and controlportion of the system are shown in FIG. 8b (the DIMS, IMS and ionizationchamber component dimensions are discussed below and in later Figures).These dimensions 23.88 cm (L), 12.86 cm (W), and 8.56 cm (H) areexemplary and one skilled in the art recognizes variations in thedimensions in order to balance multiple factors including weight,footprint, mobility and results for the intended purpose and use.

The processing system 350 as illustrated is merely intended to beexemplary. One skilled in the art recognizes that there are numerouspossible configurations and implementations for relaying data, i.e., thedata port, and processing data. For example, the data port could be awireless transmitter or a wireless transceiver wherein processing iscompleted remotely and results thereof are received back at the systemand displayed to the user on a visual or audio display mounted on thesystem 200. Alternatively, the system 200 could include the processingsystem 350 within its footprint using, e.g., microprocessing technologyon-board. In combination with a visual, auditory or tactile displaymounted on the system 200, the system 200 is a stand-alone system and,as discussed below, may be constructed so as to be hand-held.

FIGS. 9a to 9e provide more detailed views of the configuration andintegration of the IMS cells 205 a, 205 b, DIMS 210 and ionizationchamber 225 components indicated by the dotted box in FIGS. 8a . Theexploded view in FIG. 9b shows the DIMS 210 in relation to theionization chamber 225 which, in this particular embodiment, includesthe corona needle 270 and is formed of two halves, 225 a and 225 b asshown with inlet ports 235 a, 235 b (alternatively, a single inlet portis acceptable). Each half of the ionization chamber includes a gasket275 a, 275 b and bracket 280 a, 280 b for attaching to a respective IMSsensor arrays 205 a, 205 b. On the DIMS facing side of each half of theionization chamber 225, there is a partial DIMS outlet 285 b (only oneis shown) which form a full DIMS outlet (not shown) for engaging withthe DIMS ion inlet 290. Alternatively, the entirety of the DIMS outletmay be contained in a single half of the ionization chamber.

FIGS. 9c through 9e provide front, top and right side views withexemplary dimensional information. These dimensions, in centimeters, areprovided for exemplary purposes and are not intended to limit the scopeof the embodiments. One skilled in the art appreciates that variance inthe dimensions are expected and would still be considered to be withinthe scope of the invention.

And FIG. 9f provides an additional cutaway view showing two halves 225 aand 225 b of the ionization chamber with sample inlet ports 235 a, 235b, IMS outlets 300 a, 300 b, IMS sensor arrays 205 a, 205 b, DIMS outlet285, DIMS ion inlet 290 and pre-DIMS drift gas bleed-off outlets 305 a,305 b. The pre-DIMS drift gas bleed-off outlets are not a requiredfeature.

FIGS. 10a and 10b provide comprehensive views of an ionization chamber225 which, in this particular embodiment is formed of two halves, 225 aand 225 b and includes corona entry point 295, sample inlet ports 235 a,235 b (alternatively, a single inlet port may be used), DIMS outlet 285,respective IMS outlets 300 a, 300 b and a pre-DIMS drift gas bleed-offoutlet 305.

FIGS. 11a and 11b provide comprehensive views of an alternativeionization chamber 225 which, in this particular embodiment is a singlecomponent with an added top plate 310 and includes corona entry point295, sample inlet port 235, DIMS outlet 285, respective IMS outlets 300a, 300 b and an ion insulation shield 315.

During operation, additional exemplary metrics for the detection processinclude rate of drift gas supply, rate of gas bleed-off and ratesupplied to DIMS. In a non-limiting implementation, values weredetermined to be 1 L/min drift gas supply and exhaust and 290 cc/min toDIMS. One skilled in the art also recognizes that other operationalcharacteristics of the individual components are controllable to achievedesired results, including flow rates, currents/voltages,sensor/detector temperatures and the like.

The fused detector described herein is able to detect chemicals in allstates of matter in the air and on surfaces, including land, personnel,equipment and facilities. The varied capabilities included in a singledetector using some common components allows for reduced size, weightand power requirements, resulting in a single device that may be used inthe field. Additionally, the dual and parallel signal processing withback end discriminatory processing, results in better sensitivity,reduced interference and minimization of false alarms. Such fieldsincluding, but not limited to, combat, anti-terrorism, law enforcementand the like. Specific applications include, but are not limited to,site assessment for chemical hazards, site exploitation, decontaminationscreening and clearance, autonomous detection in near real-time wholemoving (e.g., on soldier, police, ship, other vehicles), outdoor andindoor monitoring for chemical hazards.

In concluding the detailed description, it should be noted that it wouldbe obvious to those skilled in the art that many variations andmodifications can be made to the embodiments without substantiallydeparting from the principles described herein. Also, such variationsand modifications are intended to be included herein within the scope asset forth in the appended claims.

It should be emphasized that the above-described embodiments are merelypossible examples of the implementations, merely set forth for a clearunderstanding of the principles of thereof. Any variations andmodifications may be made to the above-described embodiments of withoutdeparting substantially from the spirit of the principles of theembodiments. All such modifications and variations are intended to beincluded herein within the scope of the disclosure.

The present invention has been described in sufficient detail with acertain degree of particularity. The utilities thereof are appreciatedby those skilled in the art. It is understood to those skilled in theart that the present disclosure of embodiments has been made by way ofexamples only and that numerous changes in the arrangement andcombination of parts may be resorted without departing from the spiritand scope thereof.

We claim:
 1. A chemical agent detector comprising: an ionization chamberincluding at least one ion source for generating positive and negativeions from a sample received therein from a first direction; a first ionmobility spectrometry cell integrated with the ionization chamber forreceiving at least a first portion of the positive ions emanatingtherefrom in a second direction; a second ion mobility spectrometry cellintegrated with the ionization chamber for receiving at least a firstportion of the negative ions emanating therefrom in a third direction; adifferential ion mobility spectrometry cell integrated with theionization chamber for receiving at least a second portion of thepositive ions and at least a second portion of the negative ionsemanating therefrom in the first direction, wherein the sample and thedifferential ion mobility spectrometry cell are on opposite sides of theionization chamber and separated thereby and the first and second ionmobility spectrometry cells are on opposite sides of the ionizationchamber and separate thereby; and a processor for separately receivingfirst detection data from the first ion mobility spectrometry cell,second detection data from the second ion mobility spectrometry cell,and third detection data from the differential ion mobility spectrometrycell and processing the first, second and third detection data todetermine presence of one or more chemical agents in the sample.
 2. Thechemical agent detector according to claim 1, wherein the ionizationchamber further includes: a front face; a back face opposite the frontface; first and second side faces opposite one another and between,perpendicular to and connecting the front face and the back face; a topface perpendicular to and connecting the front face, back face and firstand second side faces; wherein the front face includes at least oneinput port for receiving the sample into the ionization chamber, the topface includes at least one input port for receiving the ion source, thefirst side face includes an i/o port for passing the first portion ofpositive ions to the first ion mobility spectrometry cell and receivingdrift gas into the ionization chamber from the first ion mobilityspectrometry cell, the second side face includes an i/o port for passingthe first portion of negative ions to the second ion mobilityspectrometry cell and receiving drift gas into the ionization chamberfrom the second mobility spectrometry cell, and the back face includesand exit port for passing the second portion of positive ions, thesecond portion of negative ions and the drift gas to the differentialion mobility spectrometry cell;
 3. The chemical agent detector accordingto claim 2, wherein the exit port to the differential ion mobilityspectrometry cell further includes at least one side port for allowing afirst portion of the drift gas to exit prior to entering thedifferential ion mobility spectrometry cell.
 4. The chemical agentdetector according to claim 3, further comprising first and second gasscrubbers for receiving a second portion of the drift gas after it haspassed through the differential ion mobility spectrometry cell and thefirst portion of the drift gas from the at least one side port, removingcontaminants therefrom and returning clean drift gas to the first andsecond ion mobility spectrometry cells, wherein the clean drift gasflows in an opposite direction to the first portion of positive ions andthe first portion of negative ions flowing in the first and second ionmobility spectrometry cells.
 5. The chemical agent detector according toclaim 1, wherein the ion source is a corona discharge source.
 6. Thechemical agent detector according to claim 1, further comprising a massspectrometer interfaced with an output of the differential ion mobilityspectrometry cell.
 7. The chemical agent detector according to claim 1,wherein the at least one ion source is a single ion source.
 8. Thechemical agent detector according to claim 3, wherein there are two sideports for allowing a first portion of the drift gas to exit prior toentering the differential ion mobility spectrometry cell.
 9. Thechemical agent detector according to claim 1, further comprising anindicator selected from the group consisting of audio, visual andtactile indicators for indicating when the sample contains one or morepredetermined chemical agents.
 10. A hand-held chemical agent detectorcomprising: an ionization chamber including at least one ion source forgenerating positive and negative ions from a sample, wherein thedimensions of the ionization chamber are less than 1 cm width, 2.5 cmlength and 2.0 cm height; a first and second ion mobility spectrometrycells integrated with the ionization chamber on opposite sides thereoffor receiving at least a first portion of the positive and negative ionstherefrom, wherein the dimensions of the first and second ion mobilityspectrometry cells are less than 2.5 cm width, 2.0 cm length and 2.5 cmheight; and a differential ion mobility spectrometry cell integratedwith the ionization chamber on a side thereof opposite the sample forreceiving at least a second portion of the positive ions and at least asecond portion of the negative ions therefrom, wherein the dimensions ofthe differential ion mobility spectrometry cell are less than 1 cmwidth, 1.0 cm length and 3.0 cm height.
 11. The hand-held chemical agentdetector of claim 10, the ionization chamber further including: a frontface; a back face opposite the front face; first and second side facesopposite one another and between, perpendicular to and connecting thefront face and the back face; a top face perpendicular to and connectingthe front face, back face and first and second side faces; wherein thefront face includes at least one input port for receiving the sampleinto the ionization chamber, the top face includes at least one inputport for receiving the ion source, the first side face includes an i/oport for passing the first portion of positive ions to the first ionmobility spectrometry cell and receiving drift gas into the ionizationchamber from the first ion mobility spectrometry cell, the second sideface includes an i/o port for passing the first portion of negative ionsto the second ion mobility spectrometry cell and receiving drift gasinto the ionization chamber from the second mobility spectrometry cell,and the back face includes and exit port for passing the second portionof positive ions, the second portion of negative ions and the drift gasto the differential ion mobility spectrometry cell.
 12. The hand-heldchemical agent detector according to claim 11, wherein the exit port tothe differential ion mobility spectrometry cell further includes atleast one side port for allowing a first portion of the drift gas toexit prior to entering the differential ion mobility spectrometry cell.13. The hand-held chemical agent detector according to claim 12, furthercomprising first and second gas scrubbers for receiving a second portionof the drift gas after it has passed through the differential ionmobility spectrometry cell and the first portion of the drift gas fromthe at least one side port, removing contaminants therefrom andreturning clean drift gas to the first and second ion mobilityspectrometry cells, wherein the clean drift gas flows in an oppositedirection to the first portion of positive ions and the first portion ofnegative ions flowing in the first and second ion mobility spectrometrycells.
 14. The hand-held_chemical agent detector according to claim 11,wherein the at least one ion source is a single corona discharge source.15. The hand-held chemical agent detector according to claim 11, furthercomprising two side ports located at an interface between the ionizationchamber and the differential ion mobility spectrometry cell for allowinga first portion of the drift gas to exit prior to entering thedifferential ion mobility spectrometry cell.